Semiconductor wafers are subjected to numerous steps during processing. Wafer processing usually entails transporting a plurality of wafers from one workstation to another for processing by specialized equipment. As part of the processing procedure, wafers may be temporarily stored or shipped in containers to other plants or to end-users. Movement of wafers through various environments may expose the wafers to potential wafer damaging contaminants. In order to shield the wafers from exposure to deleterious contaminants, the wafers are housed in specialized containers that not only isolate the wafers from exterior contaminants but also minimize the generation of contaminants. A common feature of these containers includes a removable door or closure which seal or are sealed, such as by tape, when closed.
As the number of circuits per unit area has increased in semiconductor wafers, each circuit has correspondingly decreased in size making contaminants in the form particulates more problematic. The size of particulates that can destroy a circuit has decreased and is approaching the molecular level. Particulate control is necessary during all phases of manufacturing, processing, transporting and storage of semiconductor wafers. The industry is moving toward processing larger and larger wafers into semiconductors. Three hundred millimeter (300 mm) wafers are now commonplace.
Wafer carriers may be made of a variety of materials, which in almost all cases comprises thermoplastics. Early containers including, enclosures and closures, were made of highly moldable plastics such as polyethelene, see U.S. Pat. No. 4,248,346. Other containers held rigid h-bar carriers such as disclosed in U.S. Pat. No. 5,273,159, while others comprised polycarbonate enclosure portions with molded in slots and softer, more resilient covers. See for example U.S. Pat. No. 5,586,658.
Most wafer containers used within semiconductor fabrication facilities have a seal interposed between the door and the housing of the wafer container. In addition, the wafer container is capable of being sealingly engaged with the processing equipment. These wafer containers are generally known as “SMIF” pods (sealed mechanical interface) or transport modules because the door closes an open bottom of the container or housing. These containers must conform to rigid structural and performance requirements because of their constant exposure to rigorous operating conditions. Further, they must be mechanically latchable by robotic or manual means and must provide exceptional isolation, such as being hermetically sealable, upon simply closing the door.
Containers used in semiconductor processing facilities for 300 mm wafers typically use front opening modules. A conventional seal for both SMIF pods and transport modules have been relatively simple elastomeric seals that are simply compressed between the door and the housing in an axial direction to provide the seal. With this approach, the polycarbonate of the housing portion that contacts the elastomeric seal may at times adhere to the seal and inadvertently damage the seal. The constant opening and closing of the door may move the seal out of position and introduce a protruding or dangling portion of the seal that can inadvertently catch a piece of processing equipment, causing catastrophic wafer breakages or can render the container unsealable.
Accordingly, a sealing arrangement is needed for wafer enclosures that enhances the hermetic seal of the wafer enclosure and inhibits movement of the elastomeric seal. A wafer enclosure sealing arrangement that addresses the aforementioned problems, as well as other related problems, is therefore desirable.